by
Lial, Margaret L.; Salzman, Stanley A.; Hestwood, Diana L.

Answer

Composite

Work Step by Step

A prime number is a whole number that has exactly two factors, itself and the number 1. Any number besides 0 and 1 that are not prime are composite.
The number 45 is not prime, because $3\times15=45$, for example. Therefore, 45 has factors besides 1 and 45, so it must be a composite number.